Currently, data communication based on wireless LAN, typified by IEEE 802.11, is generally used. For example, such data communication is adopted as signal transmitting means that replaces wired communication used in a personal computer (PC), PC peripheral devices such as a printer, a hard disk, and a broadband router, electronic appliances such as a FAX, a refrigerator, a standard-definition television (SDTV), a high-definition television (HDTV), a digital camera, a digital video camera, and a mobile phone, an automobile and an aircraft.
IEEE 802.11a, a standard of the wireless LAN, uses the OFDM (Orthogonal Frequency Division Multiplexing) modulation scheme to support high-speed data communication of bandwidth up to 54 Mbps, and uses the frequency band of 5 GHz. IEEE 802.11b adopts the DSSS (Direct Sequence Spread Spectrum) scheme to support high-speed communication of 5.5 Mbps and 11 Mbps and uses the ISM (Industrial Scientific and Medical) band of 2.4 GHz which can be freely used without radio license. IEEE 802.11g uses the OFDM modulation scheme to support high-speed data communication of bandwidth up to 54 Mbps, and similarly to IEEE 802.11b, IEEE 802.11g uses the band of 2.4 GHz. Also, WiMAX (IEEE 802.16-2004, IEEE 802.16e-2005 and the like), which has been proposed as a standard of high-speed wireless communications covering a communication distance of about several kilometers, uses the three frequency bands of 2.5 GHz, 3.5 GHz, and 5 GHz. WiMAX is expected as a technique for covering so-called the last one mile of optical communication.
In recent years, a wireless communications system based on the MIMO (Multiple-Input, Multiple-Output) scheme, which has superior communication characteristics, has received attention. The MIMO scheme needs, for each communication system, a plurality of receiving terminals that can independently carry out simultaneous receiving. Here, it is assumed that the MIMO includes the SIMO (Single-Input, Multiple-Output). In the wireless communications systems based on the MIMO scheme, since circuit configuration including receiving terminals in each communication system is increased, isolation between the communication systems is difficult as well as the circuit configuration is complex. For this reason, it is highly difficult to adopt the MIMO scheme as multiband wireless communications. In particular, in the case of WiMAX, which consumes high transmission power, the isolation between multiple communication systems is critical in order to decrease the loss of the transmission power.
For high frequency components that use a plurality of communication systems such as wireless LAN and WiMAX, it is important how to separately handle transmission/reception signals of these communication systems. For example, transmitting diversity circuits have attracted the attention as wireless communications systems. A transmitting diversity includes a plurality of antennas and can select an optimum antenna therefrom on the basis of radio wave conditions, thereby enabling the transmission power to be reduced and a mobile device to run for a long time.
Patent Literature 1 describes the use of a high frequency switch composed of a FET switch as a diversity circuit. Patent Literature 2 describes a switch circuit composed of a combination of three SPDT switches as a conventional technique. Patent Literature 2 also describes a switch into which FET switches are formed as an integrated circuit on a semiconductor chip. As a transmitting diversity circuit of a TDMA wireless apparatus including a plurality of switch circuits, Patent Literature 3 discloses a wireless apparatus in which a filter circuit is disposed at each path as shown in FIG. 1.